1. Field of the Invention
The present invention relates to a valve timing control device of an internal combustion engine, that controls or changes open/close timing of intake or exhaust valves under operation of the engine.
2. Description of the Prior Art
Some of the valve timing control devices are of a type that is arranged between a sprocket that is driven by a timing chain in synchronization with the engine rotation and a camshaft that drives intake valves or exhaust valves and arranged to rotate the camshaft in one or the other direction relative to the sprocket thereby to control or change the open/close timing of the valves.
Japanese Patent First Provisional Publication 9-324611 shows a valve timing control device which comprises a sprocket driven by a timing chain in synchronization with the engine rotation, a housing rotated together with the sprocket, a rotor installed in the housing and rotated together with a camshaft, a plurality of radially outward projecting vanes provided on the rotor in a manner to define in the housing a plurality of working fluid chambers and a charging/discharging means for charging and discharging a working fluid to and from the working fluid chambers. By actuating the charging/discharging means, a relative rotation is induced between the housing and the rotor and thus between the camshaft and the sprocket. The sprocket is integral with the housing and they are made of cast iron. The sprocket has on its outer periphery a plurality of teeth with which the timing chain is meshed.
For lubricating the sprocket and the timing chain, the lubrication oil in an oil pan is used. That is, due to rotation of a crankshaft of the engine, the oil in the oil pan is splashed over the sprocket and the timing chain. However, this oil application method has failed to obtain satisfied oil lubrication at the portion where the sprocket and the timing chain are meshed.